Last week I went to my local Gem and Mineral Society for a broom casting session. All members that were interested had a chance to do some casting using sterling silver. We melt the silver in a crucible and then when it is liquid hot we pour it into the top of a gathered cluster of broom straw or pine needles or even juniper that has been soaked in water. One member even had some palm frond material that he wanted to try and it came out really well. No two are alike, and the organic structures are wonderful to set stones into for intricate and delicate designs.
Next time I do this I will photograph the process so you can see better how it is done.
Here are some finished pieces I had cast on an earlier date, as well as some newer ones.

These pieces have natural gemstones of Amethyst, Boulder Opal, Australian Opal, Citrine, Turquoise, Alexandrite, and Swiss Blue Topaz.
I also had made a gorgeous ring but chipped the stone while setting it.
An expensive Oops!